Method of sterilizing and preserving



Patented Dec. 21, 1948 METHOD OF ST ERILIZING AND PRESERVING ArnoBrasch, Brooklyn, N. Y. assignor, by mesne assignments, to ElectronizedChemicals Corporation, a corporation of Delaware No Drawing. ApplicationSeptember 28, 1946,

Serial No. 700,167

This application is a continuation-in-part of my U; S. patentapplications Serial No. 442,136, filed May 7, 1942, for Method formanufacturing 17 Claims. (Cl. 21-54) synthetic rubber and devicestherefor; Serial No.

442,137, filed May 7, 1942, now Patent No. 2,429,217 granted Oct. 21,1947, for Devices for treatment of matters with high speed electrons;Serial No. 442,138, filed May 7, 1942, now abandoned, for Method fortreatment of matter; Serial No. 450,923, filed July 14, 1942, for Methodand means for treatment of perishable substances and products soobtained; Serial No. 451,370, filed July 17, 1942, for Method and meansfor treatment of vegetative substances and products so obtained; SerialNo. 487,179, filed May 15, 1943, now abandoned, for. Process forcracking hydrocarbons by means of ultra high speed electrons; Serial No.488,278, filed May 24, 1943, for Preparation and cracking ofhydrocarbons and other chemical compounds by means of ultra high speedelectrons to obtain rubber starting materials; andSerial No. 575,878,filed February 2, 1945, for Sterilization of therapeutical preparations.

My present invention relates to methods of sterilizing and preservingsubstances such as food stuffs and drugs.

It is an object of my present invention to sterilize and preserve foodstuffs and drugs without adversely affecting the same.

It is another. object of my present invention to sterilize and preservefood stuffs and drugs which are adversely affected by heating.

A further object of my present invention consists in methods ofsterilizing and preserving food stuffs without developingharmful sideeffects such as change of their appearance, taste and odor'a.

Still another object of my present invention consists in methods ofsterilizing and preserving drugs without developing harmful side effectssuch as reduction of their therapeutical emclency.

in creation of hydrogen peroxide, ozone and nitrous oxides, formation ofmercaptans and/or sulfides, particularly I from sulphur containingcompounds, denaturation of the proteins present in certain foodstuffs,decarboxylation, and hydrolysis of certain irradiated substances.

I have found that-the side reactions mentioned in the .precedingparagraph are mainly due to the interactions of the electrons with theatmosphere surrounding the irradiated substances and the reactivecompounds within these substances, to the production of heat and otherrelated factors, and not due to the action of the high speed electronsproper.

I have also found that these side reactions can be reduced by shorteningthe time periods during which the foodstuffs and drugs are irradiated.Therefore, sterilization and preservation processes according to mypresent invention mainly consist in irradiating the foodstuffs and drugsto be sterilized with high speed electrons during one or more extremelyshort time period. Such reduction of the length of the singleirradiation periods results in reduction or avoidance of the abovelisted undesired side reactions.

Furthermore, it is important to avoid creation of heat in the irradiatedfoodstuffs and drugs;

7 this object is also attained by reducingthe length Still a' furtherobject of my present invention 4 consists in methods of sterilizationand preservation of food stuffs and drugs which enable sterilizationand/or preservation of the same without heating or treatment with agentswhich are harmful to the treated substances.

In order to attain above objects, I have first tried to irradiate foodstuffs and drugs with high speed electrons of a velocity equivalent tomore than 1 million volts. Although micro-organisms within thepenetration range of the irradiating high speed electrons were killed,the results of such irradiations were not very satisfactory because theirradiated prpducts, showed a pronounced change in taste, odor,appearance and structure.

I have found that the side reactions causing the change in taste, odor,appearance and structure of the irradiated products. consisted mainly ofthe single irradiation periods.

I have obtained very good results by using for sterilization purposeshigh speed electrons of a velocity equivalent to more than twopreferably more than four million volts; excellent results were obtainedby use of high speed electrons of a velocity equivalent to about sixmillion volts.

The definition high speed electrons 'of a velocity equivalent to acertain voltage is intended to define high speed electrons having avelocity resulting-from the development of said voltage.

Furthermore, I have found it advisable to re-- duce the singleirradiation periods to less than 10- preferably to about 10- of ascecond. In some cases, it will even be indicated to use irra- .diationperiods each lasting 10- of a second, or less.

I wish to emphasize that the short duration of the single irradiationperiods does not change the effect of such irradiations on the germscontained in the irradiated foodstuffs or drugs; I found that suchirradiations have a sterilizing and preserving effect, i. e. destroy thegerms, inasmuch as such germs need not be killed entirely during asingle irradiation period, but only be vigorously attacked, suchattacks, particularlyif repeated during consecutive short irradiationperiods, weaken the germs which will then die or at least lose theirvirulent character a certaintime after the irradiations are actuallyterminated.

Thus, it is evident that the length of each of the single irradiationperiods is of minor importance from the point of view of destruction ofthe germs.

- but that only the total length of the irradiation periods togetherdecides the irradiation effect.

Therefore, in order to obtain optimal sterilizaserved with high speedelectrons during a series of consecutive short time periods.

I may use for my new processes described above different types ofdevices for creating high speed electrons and also the most differentlyconstructed'and shaped irradiation chambers. However, I have found thatthe devices described in my U. S. Patents Nos. 2,043,733 and 2,099,327are very well adapted and the most efflcient ones for the purposes of mypresent invention. Thus, while any source of radiation can be used forthe production of high speed electrons, my so-called condenser methodwhich generates electric impulses of very short duration and greatintensity by use of a laminated discharge tube proved most satisfactory.This method consists in using a plurality of condenser units, the numberof which is selected according to the voltage required,

charging these condenser units in parallel over charging resistances anddischarging them by means of discharge spark gaps in series whereby thevoltage is multiplied in accordance 'with the number of condenser unitsemployed and in accordance with the voltage with which each of theindividual condenser units has been charged.

This high voltage which is at least one million volts, preferablyhowever three or more million volts, is conducted to the cathode of alaminated discharge tube also described in my above mentioned U. S.patents. A discharge tube of this type is adapted to create high speedelectrons having the required high velocity and adapted for thesterilizing irradiation processes described above.

Although my above described sterilization and preservation processes-areeffective for a reat variety of foodstuffs and drugs, it is ratherdifficult to obtain satisfactory results with certain products. Thus, itis not always possible, by increase of the speed of the irradiatingelectrons and decrease of the length of the single irradiation periods,to avoid entirely certain of the above listed side effects, namely, thecreation of hydrogen peroxide, ozone and nitrous oxides, the formationof mercaptans from sulphur-containing compounds, and the denaturation ofproteins contained in some foodstuffs. Furthermore, during irradiationof certain foodstuifs and drugs, additional side reactions occur, whichcannot be eliminated by the increase of the velocity of the irradiatingelectrons and by reduction of the length of the single irradiationperiods: Such unaffected side reactions are mainly the destruction ofthe natural coloring matters in the irradiated products, particularlythe destruction of hemoglobin, chlorophylls and carotinoids present inthe irradiated substances.

I have found that the side reactions listed in the preceding paragraphcan be greatly reduced and in most cases completely avoided by coolingthe food products and drugs to be sterilized and/or preserved to a lowtemperature and irradiating the thus cooled substances in the mannerdescribed above.

The degree of cooling depends on the character of the single products tobe irradiated: Good results were already obtained by cooling to atemperature of 20-C;; the results were, however,

better if the products were cooled to a tempera ture of 100 C., or less,and irradiated at such a low temperature. I

Tests proved that by first cooling the foodstuffs and drugs to the lowtemperatures mentioned above and then subjecting the thus cooledprodnets to a series of very short irradiations by high also avoids allother above discussed side effects,-

leaving only the most rapidly occurring chemical and biologicalreactions unaifected.

It should be mentioned that during irradiation of a few products,particularly drugs, with high speed electrons, certain side reactionsoccur which can hardly be avoided by my new processes defined above.This holds true. particularly, for products which are highly unstable tooxidation such as vitamins, hormones, vaccines, quinones and likesubstances. Cooling to very low temperatures and very short irradiationperiods, as proposed above, are insufiicient to avoid oxidation of suchproducts during irradiation.

I have found it advisable to irradiate products of the type defined inthe preceding paragraph in accordance with my present invention in theabsence of oxidizing agents, e. g. in an atmosphere having an oxygenconcentration which is reduced to such a degree that'the amount ofoxygen molecules present is insufficient to react during irradiationwith the irradiated substances. Such reduction of the oxygenconcentration can be attained by use of an inert gaseous atmosphere, orby use of partial vacuum.

I have found that in order to attain permanent sterilization, it isadvisable to place the foodstuffs or drugs to be sterilized, in sealcontainers, e. g. cams for foodstuifs and ampoules for drugs, and toirradiate the products while they are sealed in such cans and ampoules.Of course, as set forth above, these containers should contain only verylittle or no oxygen at all so as to prevent oxidation of the irradiatedproducts.

In accordance with my present invention, sterilization and/orpreservation of food products and drugs is preferably carried out in thefollowing way:

First, the products to be sterilized are'placed into a container fromwhich-the air is removed,

to between three and. six million volts durin a series of consecutivevery short time periods, each lasting between 10 and 10- of a second.

I have found that from two to eighteen short irradiation periods withhigh speed electrons having a velocity equivalent to four million voltsare necessary to obtain satisfactory sterilization and/or preservationresults.

After sterilization and/or preservation of the products as describedabove, the same can be stored for a practically unlimited time withoutspoiling.

The above described sterilization process can be employed for a greatvariety of foodstuffs and drugs. Practical sterilization tests carriedout by irradiating various foodstufls and drugs with high speedelectrons of a velocity equivalent to four million volts during a seriesof consecutive irradiation periods, each lasting about of a second,showed the following results:

Diphtheria anti-toxin was irradiated once in the manner set forth aboveand became sterile without any loss of potency.

A novocalne solution was irradiated twice and became sterile without anychemical changes.

Brewers yeast infested with weevil eggs was irradiated three times andbecame sterile without any change in the yeast.

Whole bran was irradiated twice and became sterile without any change inits growth-promoting properties.

Trypsin was irradiated three times and became sterile without anyinactivation.

Ground raw beef was irradiated twice in a Pliofilm bag and becamesterile without any change in appearance, taste and odor.

Fluid milk was irradiated once and became sterile without any change inappearance.

Pork meat was irradiated four times and became 99.9% sterile without anychange in appearance.

A potato was irradiated four times and became 93.5% sterile without anychange in consistency.

I wish to note that by increasing the number of the single shortirradiation periods, it is possible not only to attain sterilization offood products and drugs, but also to attain nearly perma-- nentpreservation of the same. Thus, by increasing the number of irradiationperiods,it is possible, for instance, to attain enzyme inhibitionwithout attacking the other constituents of the irradiated foodstuffs.

In general, it can be said that by increasing the number of irradiationsto three to eighteen times the number of irradiations necessary forsterilization, enzyme inhibition and therefore preservation of theirradiated food products can be obtained without any noticeable changein taste, odor and appearance of the irradiated substances, particularlyfoodstuffs.

Practical preservation tests carried out by irradiating variousfoodstuffs in the same manner as described above in. connection withsterilization tests, but a greater number of times, showed the followingresults:

Lean beef and ground pork were irradiated eight times in the manner setforth above and then stored at incubator temperature for twelve days;after such storage time they were examined and it was found that theirappearance, taste and odor were substantially unchanged.

' Calfs liver and chicken were irradiated six to eight times and thenstored for several days; ex-

amined after such storage, they showed a fairto good appearance, tasteand odor.

An oyster was irradiated six times and then stored at incubatortemperature for iflve days and had thereafter a good appearance and odorand a fair slightly cooked taste.

Fluid milk and fluid cream were irradiated 6 six to eight times in themanner set forth above and then stored at room temperature for six riedout in an inert gaseous atmosphere and some were carried out in apartial vacuum. It was found that reduction of the temperature andavoidance of oxidizing substances greatly iniproved the sterilizationand preservation effects by\preventing undesired side reactions.

I will be understood that each of the elements described above, or'twoor more together, may

also find a useful application in other typesof sterilization andpreservation processes differing from the types described above.

While I have described the invention as embodied in processes forsterlizing and preserving foodstuffs and drugs, I do not intend to belimited to the details shown, since various modifications and changesmay be made without departing in any way from the spirit of myinvention.

Without further analysis, the foregoing will so fully reveal the gist ofmy invention. that others can by applying current knowledge readilyadapt it for various applications without omitting features that, fromthe standpoint of prior art, fairly constitute essential characteristicsof the generic or specific aspects of this invention, and, therefore,such adaptations should and are intended to be comprehended within themean-' ful side effects by bombarding the same re-.

peatedly with high speed electrons of a velocity equivalent to more thanone million volts during consecutive very short time periods eachlasting less than 10- of a second.

3. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects comprising the steps of coolingthe same to a temperature below 0 0.; and bombarding the thus cooledsubstance with high speed electrons of a velocity equivalent to morethan one million volts during at least one very short time periodlasting less than 10- of a second.

4. Method of sterilizing a substance, such as a foodstuff or a drug,without delevoping harmful side effects comprising the steps of coolingthe same to a temperature below 0 0.; and bombarding the thus cooledsubstance with high speed electrons of a velocity equivalent to morethan one million volts during consecutive very short time periods eachlasting less than 10- of a second.

. 5. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side efiects comprising the steps of coolingthe same to a temperature of below -50 0.; and bombarding the thuscooled substance with high speed electrons of a velocity equivalent tomore than one million volts during at least one very short time periodlasting less than 10- of a second.

6. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects by bombarding the same with highspeed electrons of a velocity equivalent to ing such electronbombardment oxidizing agents from the bombarded substance.

8. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harm-- ful side effects by bombarding the same in aninert gaseous atmosphere with high speed electrons of a velocityequivalent to more than one million volts during at least one very shorttime period lasting less than 10- of a second.

7 9. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects by bombarding the samerepeatedly in a partial vacuum with high speed electrons of a velocityequivalent to more than one million volts during consecutive very shorttime periods each lasting less than 10- of a'second.

10. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects by bombarding the same in asubstantially oxygen free atmosphere with high speed electrons of avelocity equivalent to more than one million volts during at least onevery short time period lasting less than 10- of a second.

11. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects comprising the steps of coolingthe same to a temperature below C.; and bombarding the thus cooled,substance in a substantially oxygen free atmosphere withhigh speedelectrons of a velocity equivalent to more than one million volts duringat least one very short time period lasting less than of a second.

12. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects comprising the steps of placingsaid substance into a container; air-tightly closing said container; andbombarding said substance air-tightly enclosed in said container withhigh speed electrons of a velocity equivalent to more than one millionvolts during at least one very short time 'period lasting less than. 10of a second.

13. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmiul side effects comprisingthe steps of placingsaid substance into a container; air-tightly clos: ing said container;and bombarding said s'ubstance air-tightly enclosed in said containerwith high speed electrons of a velocity equivalent to more than onemillion volts during consecutive very short time periods each lastingless than 10- of a second.

14. Method of sterilizing a substance, such as a foodstuff or a drug,without developing harmful side effects comprising the steps of placingsaid sdbstance into a container; air-tightly closing said container;cooling said substance airtightly. enclosed in said container to atemperature below 0 C.; and bombarding said cooled substance air-tightlyenclosed in said container with high speed electrons of a velocityequivalent to more than one million volts during at least one very shorttime period lasting less than 10- of a second. I

15. Method of sterilizing a substance, such as a foodstuff or adrug-without developing harmful side effects comprising the steps ofplacing said substance into-a container; air-tightly closing saidcontainer; cooling said substance airtightly enclosed in said containerto a temperature below 0 C.; and bombarding said cooled substanceair-tightly-enclosed.in said container with high speed electrons of avelocity equivalent to more than one million volts during consecutivevery short time periods each lasting less than 10- of a second.

16. Method of sterilizing a substance, such as foodstuff or a drug,without developing harmful side effects comprising the steps of placingsaid substance into a container; removing air contained in saidcontainer; air-tightly closing said container; and bombardingsa idsubstance air-tightly enclosed in said container with high speedelectrons of a velocity equivalent to more than one million volts duringat least one very short time period lasting less than 10" of aair'-tightly enclosed in said container with, high; speed electrons of avelocity equivalent to more than one million volts during consecutivevery short time period each lasting less than 10- of a second.

ARNO BRASCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date Number Name 924,284 Smith June 8, 1909 v1,945,867

Rawls Feb. 6, 1934 OTHER REFERENCES Principles of a New Therapy WithHigh Speed Electrons. A preliminary report by Richard Schindler MD.Reprinted from Radiology, vol. 34. No. 2, Pages 222-234, February 1940.

